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RSACryptoServiceProvider Constructor

Updated: April 2009

Initializes a new instance of the RSACryptoServiceProvider class using the default key.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

public RSACryptoServiceProvider()

ExceptionCondition
CryptographicException

The cryptographic service provider (CSP) cannot be acquired.

If no default key is found, a new key is created.

This constructor creates an Exchange key pair suitable to encrypt session keys so that they can be safely stored and exchanged with other users. The generated key corresponds to a key generated using the AT_KEYEXCHANGE value used in the unmanaged Microsoft Cryptographic API (CAPI).

Important noteImportant Note:

In the .NET Framework version 3.5 Service Pack 1 and later, when you use this constructor, the default ProviderType field that is supplied is 24 (PROV_RSA_AES). However, the ProviderName field is not supplied when ProviderType is greater than 20. To explicitly set the ProviderType to a value that supplies the ProviderName, use the RSACryptoServiceProvider(CspParameters) constructor, which takes a CspParameters parameter, and set its ProviderType field to a value that is less than 20, for example, 1 (PROV_RSA_FULL).

The following code example uses the RSACryptoServiceProvider class to encrypt a string into an array of bytes and then decrypt the bytes back into a string.

using System;
using System.Security.Cryptography;
using System.Text;

class RSACSPSample
{

    static void Main()
    {
        try
        {
            //Create a UnicodeEncoder to convert between byte array and string.
            UnicodeEncoding ByteConverter = new UnicodeEncoding();

            //Create byte arrays to hold original, encrypted, and decrypted data.
            byte[] dataToEncrypt = ByteConverter.GetBytes("Data to Encrypt");
            byte[] encryptedData;
            byte[] decryptedData;

            //Create a new instance of RSACryptoServiceProvider to generate 
            //public and private key data. 
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {

                //Pass the data to ENCRYPT, the public key information  
                //(using RSACryptoServiceProvider.ExportParameters(false), 
                //and a boolean flag specifying no OAEP padding.
                encryptedData = RSAEncrypt(dataToEncrypt, RSA.ExportParameters(false), false);

                //Pass the data to DECRYPT, the private key information  
                //(using RSACryptoServiceProvider.ExportParameters(true), 
                //and a boolean flag specifying no OAEP padding.
                decryptedData = RSADecrypt(encryptedData, RSA.ExportParameters(true), false);

                //Display the decrypted plaintext to the console. 
                Console.WriteLine("Decrypted plaintext: {0}", ByteConverter.GetString(decryptedData));
            }
        }
        catch (ArgumentNullException)
        {
            //Catch this exception in case the encryption did 
            //not succeed.
            Console.WriteLine("Encryption failed.");

        }
    }

    static public byte[] RSAEncrypt(byte[] DataToEncrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
    {
        try
        {
            byte[] encryptedData;
            //Create a new instance of RSACryptoServiceProvider. 
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {

                //Import the RSA Key information. This only needs 
                //toinclude the public key information.
                RSA.ImportParameters(RSAKeyInfo);

                //Encrypt the passed byte array and specify OAEP padding.   
                //OAEP padding is only available on Microsoft Windows XP or 
                //later.  
                encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
            }
            return encryptedData;
        }
        //Catch and display a CryptographicException   
        //to the console. 
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);

            return null;
        }

    }

    static public byte[] RSADecrypt(byte[] DataToDecrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
    {
        try
        {
            byte[] decryptedData;
            //Create a new instance of RSACryptoServiceProvider. 
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {
                //Import the RSA Key information. This needs 
                //to include the private key information.
                RSA.ImportParameters(RSAKeyInfo);

                //Decrypt the passed byte array and specify OAEP padding.   
                //OAEP padding is only available on Microsoft Windows XP or 
                //later.  
                decryptedData = RSA.Decrypt(DataToDecrypt, DoOAEPPadding);
            }
            return decryptedData;
        }
        //Catch and display a CryptographicException   
        //to the console. 
        catch (CryptographicException e)
        {
            Console.WriteLine(e.ToString());

            return null;
        }

    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0

Date

History

Reason

April 2009

Added advisory note about constructor.

Content bug fix.

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